Reverse-current device.



NoI 848,944. PATENTED APR. 2, 1907.

l E. B. WEDMORE.

REVERSE CURRENT DEVICE.

AIPLIUATION FILED NOV. 11,1905.

/ /mll di I fl y /f HII/ mi .gq ik WFA/55.55. EdYmhO//VME/N ait-t EDMUN D B. WEDMORE, OF RUGBY, ENGLAND, AASSIGrNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION -OF NEW YORK.

REVERSE-CURRENT DEvloE. I

To all lwhom it may concern:

Be it known thatv I, EDMUND B. WEDMORE, a subject of the King lci Great Britain, residing at Rugby, En land, have invented certaln new and use l Improvements in Reverse-Current Devices, ofwhich the following is a specification. My invention relates particularly to electromagnetic devices used in connection with electric-circuit breakers for causing the operation of a circuit-breaker upon reversal of thc current in a Vcircuit or circuits controlled thereb In tllie form of this device now commonly used a current and a potential coil aro arranged to act on'a magnetic plunger, the two coils being op osed to one another when the direction of the current in the circuit upon which they are connected is normal and assisting each other upon reversal of current, so

' as to move the plunger and cause the "o ening of an automatic circuit-breaker. Suc 1 a device will be caused to operate by the flow of suflicientcurrent in the normal direction, the magnetizlng eect "of the series coil being suflicient to overcome that of the shunt-coil and to provide in addition the necessary magnetic lux to o crate the plunger. It 1s commonly desirab e to obtain a relatively low setting ofthe device for operation on re verse current and high setting for operation current device.

The

on'overloads in theA normal direction.

i ratio between the overload and reverse-eurrentsetting may be increased by so pro 701?- tiomng the potential-Winding that on y e small'increase 'of magnetizing force is required to cause the device to operate. This adjustment is accompanied b two disadvantages. First, the device is lia le to operate on a rise of potential occurring and inde endently of reversal of current; secondly, t e reverse current required to cause the device -to operate .will be greatly increased should the otential be much reduced below normal va ue.

The main object of my invention is to provide improved means for increasing the ratio between the overload and reverse-current settings in which the disadvantages accompanying lthe above adjustment are materially reduced. a

A further object of the invention is to 0btain a proportional adjustment, of the overload andreverse-current settings of a reverse- Specification of Letters Patent. Application led November 11,1905. Serial-Nn. 286,843.

Patented April' 2, i907.

'The invention is intended to bel applicable more-particularly for reverse-current devices used on alternating-current' circuits, and is designed also for overcomin some of the disadvantages peculiar .to`.dev1ces' of this kind. It will be obvious, however, that inl some of its features the invention isapplicable to devices for-use on continuous-current circuits.

Referring to the accompanying drawins,l in which li el arts are designated 'by t e. same referenceetters, Figure lis a sectional elevation of a reverse-current device constructed according to one form of my invention, and Figs. 2 and 3 are similar views of modified forms of device.

I constructE the reverse-current device in the usual forni of acompound-wound Aironclad` solenoid consisting "of a cylindricalv iron casing a, secured to a suitable support, asc',

and having a removable-iron cover b, niclos'- ing a air of windings c and d. The winding c is a apted to carry the main current in a supply-circuit or a current proportional theret0, d the'wiuding d is adapted to. be connested across the terminals of the circuit or in' the case of high-tension alternating-current electric circuits to be supplied from the Secondary of apotential-transformer connected across the circuit. The solenoid is fitted round a central tube c, of brass or other suitable material, whichA is secured at its lower end into the bottom 'of the casing a. Partei thecoreff is attached .tothe cover b and projects along the axes of the two coils, its iree extremity being separated by an airap g from a movable iron plunger h, located ma uide-tube'iand supported on an adjusta )le screw-glug j. vice is regulate by adjustment of the length of. the air-.ga g by screwing up or down the plug QOSely-fitting plunger 7c passes axially throu li` and projects at both ends from the fixe eoref of thesolenoid. One

The setting of the deend of this plunger is fitted with a contact Z, g

breaker-detaining catch is effected by the pin*- n, which moves with the plunger h in a'slot o, formed in theguide-tube i. The movement of the plunger h 'in Fig. 1 for causing the cirf cuit-breaker to operate by engagement with the plunger k is cushioned by the spring p,

'attached'to the lower end of the plunger c.

In devices of this kind it has been custom ary to arrange the series coil in close proxilnity to or around the air-gap, separating the fixed core from the movable plunger.

According to my invention I dispose the' windings of the potential-coil d around Ithe air-gap g and place the current-coil around a portion of the core or in general of the magnetic circuit remote from the air-gap. In the igures the current-coil c is arranged around the-fixed part of the core By this means We promote magnetic lea age of the lux due to the series-solenoid across those portions of the magnetic circuit between the series solenoid c and the air-gap g. On the occurrence'of an overload the magnetic flux density in the portion of the magnetic circuit skilled in the art, or I may employ an iron ution-of themagnetic flux. o

ring g, located between the two windings, so as to increase the leakage, as' shown in Fig. 1 or as an alternative I may employ a shortcircuited winding consisting of a metal ring 1', surrounding the core f, as shown in Fig. 3, orthe core f, which in a device for use with alternating currents is laminated, ma be made solid, so that theeddy-currents Wi l be produced init, which will modify the distri- I-.may so roportion the of the Inova le lunger h a jacent to the airgapshall be flus with or sunk below the bottom. of thev iron casing a, surrounding the solenoid, as shown in Fig. 2, thus increasing the tendency for the magnetic flux to leak to parts of the casing and away from the movable plunger. In this case the Hux from the current-coil c is distributed over the inside of the casing a and little of it reaches the plun- 1ger k on 'overloads owever, the lpotential-coil d acts lin the same direction ast to the plunger. I v

By means of my invention,as above described, I am enabled on installations where parts that the end the maximum obtainable overload-current is not too great to put the overload setting outside the possible range of operation and at the same time to enable thedevice to operate on reversal of current accompanied by a large drop of potential without necessitating the On reversal of current,

e coilc and directs the flux on` flow of so large a reverse-current as has been necessary 1n devices of the kmd described above hitherto used. Furthermore, m in-' vention, as-illustrated more particular y in Fig. l, may be used for the purpose of obtaining a proportional adjustment of the overload and reverse-current settings where it is desired that the device shall operate both on reversal of current' and on overloads.

In the ordinary form of reverse-relay ofthe solenoid type in which the two windings are uniformly disposed about the gap instead of being separated, as in my invention, a small reduction of the gap will greatly alter the reverse current-settingand only slightly alter the overload setting. Accordinfy to the devices already described so much leakage for the flux due to the current-winding on overloads is introduced as to put the overload setting very high and in some cases out of range, as already pointed out. An intermediate stage between the two extremes is obtainable, 1n which the overload adjustment is rapidly raised as the gap is reduced in length. By suitably proportioning the arts the overload adjustment may be cause to alter at the same rate approximately as the reverse-current adjustment. So long as one adjustment only is used it is necessary that the same should affect either only the reverse-current setting or only the overload setting or should affect them both in some useful and readilycomprehensible manner.l In the ordinary any appreciable alteration of the overload setting, while the reverse setting is readily altered. Y

I have found it apparently impossibleto obtain a very wide ran e of adjustment on the overload setting wit out altering the re-- verse-current setting; but a practically useful combination can be realized, as .shown in Fig. 1, which affords a proportionate simultaneous adjustment of the two settings, the leakage being obtained by the iron ring g, forming a shunt to the flux of the coil c. Thus a relay operating on, say, one-ifth normalload reverse-current and three times normal-- load overload. may be adjusted by mo "ng the plunger so as to operate on overload o say, six times normal load and onareversecurrent with the same setting of two-lifths normal load.

What I claim as new, and desire to secure by Letters Patent of the United, States, is-

1'. An electric protective dev1ce comprising current and potential coils, .and an open .differential relay it is impossible to obtain IOO magnetic circuit threading said coils and havf ing an adjustable air-gap more remote from the current-coil than from the potential-coil.

2. An electric protective device comprising current. and potential coils, an open magnetic circuit threadinglsaid coils and inclu ing a movable member, and means for promoting magnetic leakage .of the flux of one neticcircuit threading said coils and having its air-gap dis osed nearer to one coil than the other, an( means for promoting magnetic leakage of the flux of the more remote coil away from said air-gap.

6. An electric protective device comprising current and potential coils, an open magnetic circuit threading said coils and having its air-gap disposed more remote from' the current-coil than rom the potential-coil, and means for promoting magnetic leakage of the current-coil away from said gap.

7. An electric protective device comprising a casing of magnetic material, current and potential coils contained therein, a fixed core attached to the to of the casin around which the current-coi is arrange and a plunger movable within the otential-coil i and normally situatedwith its upper extremity remote from the current-coll.

8. An electric protective device comprising a casing of magnetic material, current and potential coils therein, a lixed core attached to the top of the casing and extending downward Within the current-coil, a plunger movable within the potential-coil and normally situated with its up er extremity remote rom the current-co1 and a short-circuited winding on the fixed core for shunting the flux of the current-coil.

9, An electric protective device compris- 1n current and potential coils, a fixed core of 'gh reluctance extending into one of said coils, and a cooperating plun er.

10. An electric protective evice comprising current and potential coils, an open magnetic circuit threading said coils having the core embraced by the current-coil of high reluctance.

In witness whereof I have hereunto set my hand this 36th day of October, 1905.

E. B. WEDMORE.

Witnesses:

'-VALTER W. BALL, l. Hoon. 

